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Low-profile water heating
Add water underfloor heating above a suitable existing structural floor without the depth and drying time of a traditional screed.
Compare three overlay systems designed for renovations, extensions and projects where floor build-up needs careful control.
At a glance
Compare board construction and typical uses, then open the system guide for the full specification. Board thickness excludes preparation, fixing materials and the floor finish.
| Comparison criteria | AD-CXPS | AD-EPS400 | AD-SLIM |
|---|---|---|---|
| Best starting point | Versatile retrofit projects | Lightweight insulated overlays | A firm, dense dry overlay |
| Board construction | Cement-coated XPS | Foil-faced EPS400 | High-density gypsum |
| Board thickness | 18mm or 20mm | 20mm | 18mm |
| Insulation role | Insulating XPS core | Insulating EPS core | Assess insulation beneath the board |
| Typical base | Prepared solid or timber floor | Dry, level solid or timber floor | Prepared, stable structural floor |
| Floor-finish preparation | Direct tiling with specified materials; other finishes need the approved preparation layers. | Floating wood or laminate, or tiling with specified materials; check preparation for other finishes. | Tiles and other approved finishes with the specified preparation layers. |
| Explore system | View AD-CXPS | View AD-EPS400 | View AD-SLIM |
Another retrofit option
For a small room or occasional floor warming, electric heating may be simpler to install. Compare the installation work, available floor height and likely running costs.
Often a good fit
Electric mats or cable can avoid adding a manifold and water connections for one room. A qualified electrician must make the final electrical connection.
Useful when height matters
Thin heating elements can help where height is limited. Include any insulation, membrane, levelling layer and floor covering when comparing the complete build-up.
Compare lifetime costs
Electric heating often costs less to install. For larger areas heated regularly, compare running costs with a water system connected to your proposed heat source.
Plan the complete construction
Overlay systems are useful when adding water underfloor heating above an existing floor, but the base, heat source and final finish must all be checked before ordering.
The exact layers vary by system and floor finish. Always follow the current system and flooring manufacturers’ instructions.
Overlay heating advice
Answers to the main questions about floor height, suitable bases and choosing an overlay water heating system.
Overlay water underfloor heating uses pre-routed panels installed above a suitable existing structural floor. Water pipe is pressed into the channels before the specified preparation layers and finished floor are added.
AD-CXPS boards are available in 18mm or 20mm, AD-EPS400 panels are 20mm, and AD-SLIM boards are 18mm. These are board thicknesses: preparation, fixing materials, any additional layers and the floor covering add to the finished height.
AD-CXPS uses robust cement-coated XPS; AD-EPS400 offers a lightweight foil-faced insulating board; and AD-SLIM uses dense gypsum boards for a firm dry overlay. Choose according to the existing floor, insulation, available height and intended finish, then confirm the heat-loss and system design.
It can be installed above a suitable existing structural floor once that base has been assessed and correctly prepared. Existing decorative floor coverings may need to be removed, and the base must be stable, dry and level enough for the selected system.
Direct tiling is possible with selected systems when the specified preparation, compatible adhesive and tile finish are used. Other finishes can require a levelling, overlay or separation layer.
Yes. Floor area alone does not confirm that the system can meet the room demand. The design should consider room heat loss, usable heated area, water temperature, pipe layout, controls and the thermal resistance of the finished floor.
